1. Field
One or more embodiments relate to a compound including a phosphorescence unit, an emitting polymer formed from the compound, and an organic light emitting device having an organic layer including the emitting polymer.
2. Description of the Related Art
Organic light emitting devices (“OLEDs”), which include a pair of electrodes and an organic layer interposed between the electrodes, are active light emitting display devices that emit light by recombination of electrons and holes injected through the electrodes in an organic layer when a current is applied to the organic layer through the electrodes. The OLEDs provide advantages such as lightweight, simple components, an easy fabrication process, excellent image quality, and wide viewing angles. In addition, the OLEDs can create perfect or near-perfect dynamic images and high color purity. The OLEDs also have electrical properties that are suitable for portable electronic equipment such as low power consumption and low driving voltage.
An OLED can have a structure formed as follows. An anode is formed on a substrate. A hole transport layer (“HTL”), an emitting layer (“EML”), and an electron transport layer (“ETL”), as organic layers, are sequentially formed on the anode. A cathode is formed thereon.
When a current is supplied to an anode and a cathode, holes injected from the anode are transported to the EML through the HTL, and electrons injected from the cathode are transported to the EML through the ETL. The transported holes and electrons are recombined in the EML to generate excitons. The radioactive decay of the excitons result in light emission, the light having a wavelength corresponding to a band gap of the molecule in the EML.
A material that is used to form an EML of an OLED can be classified as a fluorescent material using singlet excitons or a phosphorescent material using triplet excitons according to light emitting mechanisms. An EML can be formed using the fluorescent material or the phosphorescent material, or using a host material doped with the fluorescent material or the phosphorescent material. If the EML is formed using a host material, single excitons and triplet excitons are formed in the host material as a result of electron excitation. In this case, the singlet excitons and the triplet excitons are formed in a volume ratio of 1:3.
In an OLED using a fluorescent material for the formation of an EML, triplet excitons generated in a host are not used. However, in an OLED using a phosphorescent material for the formation of an EML, not only singlet excitons but also triplet excitons are used, thereby increasing internal quantum efficiency to 100%.
However, there is still a need to develop a high efficiency emitting material using phosphorescence that can be appropriately used for a high efficiency full color display or low power consumption white emitting device.